Islam’s most important prophet. Because Muslims believe Islam existed before Muhammad, they consider him to be the religion’s final prophet, not its founder. Non-Muslims refer to Muhammad as the founder of Islam. Capitalize the word prophet when used with Muhammad’s name – as in the Prophet Muhammad – but not when used alone. According to traditional biographers, Muhammad was born circa 570 in Mecca and died in 632 in Medina, both cities in what is now Saudi Arabia.